Tennis racket

ABSTRACT

A tennis racket includes a head including a frame surrounding a netting of string, a holding handle ( 2 ), a vibration sensor ( 14.1 ), a triaxial linear acceleration sensor ( 14.2 ), and a triaxial angular speed sensor ( 14.3 ).

The present invention relates to a tennis racket.

When a player plays tennis, it is advantageous to be able to analyze his performance, for example to evaluate and/or improve his playing technique.

US-A-2006/0025229 discloses a system for measuring the movement of a tennis racket, including a biaxial linear acceleration sensor and a triaxial angular speed sensor. This system does not make it possible to conduct satisfactory measurements of the movements of the tennis racquet.

The invention proposes an improved tennis racket making it possible to measure parameters for analyzing movements and hits by the player.

To that end, the invention relates to a racket that includes:

a head including a frame surrounding strings, a gripping handle, a vibration sensor, a triaxial linear acceleration sensor and a triaxial angular speed sensor.

Owing to the invention, the vibration, angular speed and linear acceleration measurements make it possible to obtain measurements of parameters relative to the player's performance. These parameters are recorded by the racket and can be transferred to an analysis unit such as a computer, a graphic tablet or a smart phone that processes the data recorded by the racket. The racket according to the invention is light. Furthermore, it has a satisfactory autonomy and mechanical strength.

According to advantageous but optional aspects of the invention, such a racket may incorporate one or more of the following features, considered in any technically allowable combination:

The tennis racket further includes means for storing data recorded by the sensors and means for transmitting data recorded by the sensors, in particular wired connecting means, preferably an electrical connector of the USB type, and/or wireless transmission means, preferably an antenna of the Bluetooth type.

The vibration sensor is fastened to the head of the racket, in particular by adhesion.

The head includes connecting branches that connect the strings to the handle and the vibration sensor is fastened on a connecting zone of the connecting branches.

The triaxial linear acceleration sensor and the triaxial angular speed sensor are secured to the handle.

At least one electrical circuit associated with the sensors is fastened to a removable housing that is removably fastened to the frame of the racket.

At least one of the sensors is also fastened to the removable housing.

The handle is hollow and contains the removable housing.

The electronic circuit is equipped with the triaxial linear acceleration sensor and the triaxial angular speed sensor and fastened to the removable housing.

The removable housing is fastened to the frame of the racket using fastening elements, such as screws.

The fastening elements are oriented perpendicular to the handle.

The hollow body of the handle comprises two inner rails parallel to the handle and the removable housing comprises two longitudinal slots.

The tennis racket further includes a butt cap fastened to the housing, at the free end of the handle, using removable fastening means oriented parallel to the handle.

The tennis racket further includes a rechargeable battery that powers the electronic circuit.

The racket further includes a butt cap that is fastened to the housing, at the free end of the handle, and that tightly closes the handle while allowing the control buttons of the electronic circuit to be manipulated.

The vibration sensor is secured on the frame of the racket and is connected, using electrical wires or an electrical contact provided on the removable housing, to an electronic circuit fastened to the removable housing.

The invention will be better understood and other advantages thereof will appear more clearly in light of the following description of two embodiments of a racket according to the invention, provided solely as an example and done in reference to the appended drawings, in which:

FIG. 1 is a front view of a racket according to the invention;

FIG. 2 is a partially exploded perspective view of the racket of FIG. 1;

FIG. 3 is an enlarged view of detail III in FIG. 2;

FIG. 4 is a partially exploded perspective view of the handle of a racket according to a second embodiment of the invention;

FIG. 5 is an enlarged exploded perspective view of the handle of FIG. 4, during assembly;

FIG. 6 is a view along arrow F6 in FIG. 5; and

FIG. 7 is a view similar to FIG. 6, in the assembled configuration of the handle.

FIGS. 1 to 3 show a tennis racket 1, which traditionally includes a handle 2 connected to a head T including a frame 4 inside which strings (not shown) are stretched, made up of various transverse and longitudinal cords. The head T also includes two connecting branches 6 extending divergently from the handle 2 toward the frame 4. At a connecting zone R of the head T with the handle 2, the connecting branches 6 are secured to each other.

The handle 2 includes a hollow and globally tubular body 21, for example made from carbon. Traditionally, the body 21 is covered with a thickness of foam surrounded by a grip, to improve the hold on the handle. The body 21 of the handle 2 comprises a proximal longitudinal end 21.1, situated on the side of the strings and connected to the connecting branches 6, and a distal longitudinal end 21.2, free and opposite the end 21.1. The end 21.2 is covered by a butt cap 22, which allows the player's hand not to slide off the handle 2. The butt cap 22 includes a body 221 covered by a cover 223 assembled with the body 221 by snapping. Thus, the user can easily remove the cover 223, without using tools. Furthermore, flexible fastening elements, not shown, connect the cover 223 to the body 221, to avoid separating the cover 223 from the racket 1 during use of the racket 1.

The racket 1 is equipped with a system for measuring game parameters, including a vibration sensor 14.1 that is fastened on the connecting branches 6, at the connecting zone R, in particular by adhesion. The vibration sensor 14.1 is for example a piezoelectric sensor, which measures the deformations generated by the vibrations of the racket 1. Alternatively, it may be an accelerometer calibrated on the vibration frequencies, in particular from 100 Hz to 600 Hz.

The vibration sensor 14.1 is covered by an end part 23 of the body 21 of the handle 2, surrounded by an attached ring 24, generally referred to as a “front cap”.

The vibration sensor 14.1 is connected to the electronic circuit 20, using electrical wires (not shown) housed in the body 21 of the handle 2. The electronic circuit 20 is mounted on plates fastened in a housing 16 made from a plastic material, which is housed inside the body 21, on the side of the free end 21.2 of the body 21. The housing 16 includes a body 16.1 as well as an elongated cover 16.2. The cross-section of the body 16.1 is globally U-shaped and the cover 16.2 closes the open side of the body 16.1. Screws are used to fasten the cover 16.2 to the body 16.1.

Alternatively, the electrical wires are replaced by an electrical contact for a housing 16 and which receives the vibration sensor 14.1 in contact when the housing 16 is inserted in the handle 2.

On the side of the free end 21.2 of the handle 2, the body 16.1 of the housing 16 includes a transverse plate 16.4 perpendicular to the handle 2, the geometry of which is substantially identical to the section of the body 21 of the handle 2. The electronic circuit 20 is mounted on a longitudinal plate 20.1 positioned in the volume of the housing 16, as well as on a transverse plate 20.2 fastened to the outside of the housing 16, on the transverse plate 16.4 of the housing 16, and perpendicular to the plate 20.1.

The transverse plate 16.4 of the housing 16 comprises an opening 16.6 provided for the insertion of the longitudinal plate 20.1 of the electronic circuit 20 into the housing 16, for the assembly of the electronic circuit 20 into the housing 16.

A rechargeable electric battery 18 is assembled to the cover 16.2 of the housing 16, by snapping, and powers the electronic circuit 20 via electrical wires (not shown).

The longitudinal plate 20.1 of the electronic circuit 20 bears a triaxial linear acceleration sensor 14.2, which measures the acceleration of the racket 1, as well as a triaxial angular speed sensor 14.3, which measures the speed of rotation of the racket 1. The sensors 14.2 and 14.3 measure the acceleration and the angular speed in three directions X, Y and Z perpendicular to each other, fixed relative to the land reference.

The sensors 14.1 and 14.2 are fastened to the housing 16, since they are fastened to the electronic circuit 20, the electronic circuit 20 being fastened to the housing 16. Alternatively, the sensors 14.1 and 14.2 are fastened on the racket 1, while the circuit 20 is fastened to the housing 16.

The electronic circuit 20 comprises a memory (not shown) that records the measurements of the sensors 14.1, 14.2 and 14.3.

The transverse plate 20.2 bears three control buttons 15.1, 15.2 and 15.3, allowing the user to control the system for measuring game parameters, as well as diodes 13 that light up with different colors based on actions by the user on the control buttons 15.1, 15.2 and 15.3.

The longitudinal plate 20.1 bears wireless communication means, formed by a Bluetooth antenna 11 able to transmit and receive data aerially. Furthermore, the longitudinal plate 20.1 is electrically connected to a female electrical connector 17 of the USB type, which passes through the transverse plate 20.2 and is provided to connect the racket 1 to an analysis unit by a wired connection. To respond to space concerns, the connector 17 may be of the mini-USB or micro-USB type. Thus, the racket 1 is able to communicate by wired or aerial connection with a computer, a smart phone or a graphic tablet.

The transverse plate 20.2 is covered by a flexible element 5 comprising openings 51 and 52 positioned at the connector 17 and diodes 13, to allow access to the connector 17 and visibility of the diodes 13, as well as raised portions 53.1 and 53.2 positioned at the control buttons 15.1 and 15.2 provided to improve the manipulation of the buttons 15.

On the side of the end 21.2, four small metal plates 19 are fastened to the body 21 of the handle 2.

The various components of the handle 2 are assembled by inserting the small plates 19 into the flat housings 21.3. Then, the housing 16 is inserted into the inner volume of the body 21 of the handle 2, on the side of the free end 21.2. The transverse plate 16.4 of the housing 16 then abuts against the free end 21.2 of the handle 2.

The housing 16 is removably fastened to the frame 4 of the racket 1. In other words, the housing 16 can be disassembled. More specifically, the housing 16 is removably fastened to the handle 2. Four transverse screws 3 oriented perpendicular to the handle 2 are used to fasten the small plates 19 and the housing 16 to the body 21 of the handle 2. The screws 3 are inserted into holes 21.4 made in the body 21 of the handle 2, at the free end 21.2. The screws 3 pass into holes 19.1 arranged in each small plate 19 and engage with holes formed in the housing 16. The small plates 19 make it possible to improve the anchoring of the screws 3 in the body 21 of the handle 2, given that the walls of the body 21 are relatively thin.

The screws 3 constitute removable fastening means making it possible to fasten the housing 16 to the frame 4 of the racket 1. Alternatively, other removable fastening means can be used.

Thus, it is possible to disassemble the housing 16 without damaging the racket 1, which makes maintenance of the housing 16 easier. Furthermore, the housing 16 being removable makes it possible to recycle the various parts of the racket 1. Furthermore, this makes it possible to manufacture several identical housings 16 and to assemble them different rackets, which is cost-effective.

The electronic circuit 20 is assembled to the housing 16 by sliding the longitudinal plate 20.1 into the opening 16.6 of the housing 16. The transverse plate 20.2 of the electronic circuit 20 then abuts against the transverse plate 16.4 of the housing 16. The flexible element 5 is positioned against the transverse plate 20.2 of the electronic circuit, and the body 221 of the butt cap 22 is inserted around the free end 21.2 of the body 21 of the handle 2.

Four longitudinal screws 7, oriented parallel to the handle 2, are used to fasten the butt cap 22 to the housing 16. The longitudinal screws 7 each successively pass in a hole 222 arranged in the body 221 of the butt cap 22, in a hole 53 of the flexible element 5, in a hole 20.3 of the transverse plate 20.2 of the electronic circuit 20, and in a threaded hole 16.5 of the transverse plate 16.4 of the housing 16. Thus, the butt cap 22 is secured to the housing 16 and the electronic circuit 20 is kept between the butt cap 22 and the housing 16. The butt cap 22 is therefore secured to the body 21 of the handle 2, by means of the housing 16.

After the four longitudinal screws 7 are placed, the cover 223 of the butt cap 22 is fastened to the body 221 of the butt cap 22. The materials of the cover 223 and the part 5 allow the light from the diode 13 to be seen from the outside. In order to connect a cable to the electrical connector 17, the user removes the cover 223 from the butt cap 22.

Traditionally, weights may be fastened to the housing 16 to balance the racket 1.

The antenna 11 is outside the body 21 of the handle 2, which allows it to transmit and receive signals without the material of the body 21 constituting a barrier.

The racket 1 has a reduced mass and a good mechanical strength. Furthermore, the handle 2 is tight.

The rest of the description pertains to a method for measuring and computing game parameters, using the racket 1.

In a prior step a), behavioral data of the racket 1 is generated during tests, by measuring the vibrations, the linear acceleration and the angular speed of the racket, using sensors 14.1, 14.2 and 14.3, for different parameters of the player's hits, when specific types of strokes are used (topspin forehand, serve, underspin backhand, etc.).

Each hit is characterized by several parameters. For example, a first parameter is the type of stroke (forehand, backhand or serve), determined based on the linear acceleration of the racket 1 and its angular speeds.

A second parameter is the type and quantity of effect (lift, slice or flat shot), determined based on the ratio between the angular speed of the upward movement and the forward movement of the racket 1, just before the hit.

A third parameter is the hit power, determined at the time of the hit, based on the linear acceleration and the angular speeds of the racket 1.

A fourth parameter is the location of the impact zone of the ball on the strings 8, determined based on the measurements from the three sensors 14.1, 14.2, 14.3. The strings 8 can be divided into several zones depicted in FIG. 1: a central zone Ml, which is globally circular, and four peripheral zones M2, M3, M4 and M5 that divide the remaining part of the strings 8 into four quarters: a top quarter M2 situated between the central zone M1 and the end of the frame 4 opposite the handle 2, a bottom quarter M4 situated between the central zone M1 and the part of the frame 4 connected to the connecting branches 6, and two side quarters M3 and M4 situated on either side of the central zone Ml, between the top M2 and bottom M4 quarters. Alternatively, the breakdown of the zones and the number of zones can be different.

The behavioral data is stored in a memory of the analysis unit and indicates the vibrations, linear acceleration and angular speed of the racket 1 for each parameter.

In an initialization step b), the player turns on the racket 1 and starts recording game data, using the button 15.1.

Then, in a game step c), the player hits balls, while the sensors 14.1, 14.2 and 14.3 record, in the memory of the circuit 20, game data relative to the vibrations, angular speed and linear acceleration of the racket 1.

In a transmission step d), which occurs after or during step b), the game data is sent to an analysis unit, by wireless connection, using the connector 17, or aerially, using the antenna 11. For example, the wired connection can be used at the end of the match and the aerial route can be used in real time, during the game, to communicate the data to a trainer.

Lastly, in an analysis step e), the analysis unit compares the game data and behavioral data of the racket 1 and determines, from that comparison, at least one parameter characterizing the player's movements and hits. For example, the analysis unit uses at least one of the parameters previously described. It is thus possible to determine whether the player has performed a forehand, backhand or serve, if an effect was placed on it and to what extent, the power of the hit and the impact zone of the ball on the strings 4.

FIGS. 4 to 7 show a racket handle 102 according to a second embodiment of the invention, for which elements similar to those of the racket 1 bear the same numerical references. Hereinafter, we will not describe elements similar to those of the racket 1.

The handle 102 includes a hollow body 21, which comprises two inner rails 31 and 32 parallel to the handle 102.

The handle 102 includes an elongated housing 16 with a rectangular section, in which an electronic circuit (not shown) is fastened. The housing 16 comprises two longitudinal slots 41 and 42.

Reference d1 denotes the distance between the rails 31 and 32 of the handle 2, and h1 denotes the height of the section of the inner volume of the body 21 of the handle 2, measured perpendicular to the distance d1. The distance d1 is smaller than the height h1. The rails 31 and 32 extend along a plane P1.

Reference d2 denotes the distance between the bottom of the slots 41 and 42 of the housing 16, and h2 denotes the height of the section of the housing 16, measured perpendicular to the distance d2. The distance d2 is greater than the height h2. The slots 41 and 42 extend along a plane P2.

The distance h2 is slightly smaller than the distance d1. The distances d1 and d2 are equal, to within any play.

In order to assemble the housing to the body 21 of the handle 102, the housing 16 is inserted into the volume of the body 21 of the handle 2, orienting the plane P1 perpendicular to the plane P2, as shown in FIGS. 5 and 6.

The housing 16 is pushed into the body 21 of the handle 102 until it completely protrudes past the end of the rails 31 and 32 opposite the free end 21.2 of the body 21.

Then, the body 16 is rotated by a quarter revolution around a longitudinal axis of the housing 16, which is aligned with the direction of the body 21 of the handle 102. The planes P1 and P2 are then aligned.

Then, as shown in FIG. 7, the housing 16 is translated toward the free end 21.2 of the handle 2, so as to slide the rails 31 and 32 of the handle 2 in the slots 41 and 42 of the housing.

The housing 16 is then locked in rotation, around its longitudinal axis, by the rails 31 and 32 of the body 21 of the handle 2.

A butt cap 22 is fastened to the body 21 of the handle 2, using screws (not shown), to lock the translation of the housing 16 relative to the body 21, along the longitudinal axis of the housing 16 and in a direction opposite the head of the racket.

The housing 16 is removably fastened to the frame 4 of the racket 1. In other words, the housing 16 can be disassembled. More specifically, the housing 16 is removably fastened to the handle 2.

The screws used to fasten the butt cap 22 to the body 21, associated with the rails 31 and 32 that cooperate with the slots 41 and 42, constitute removable fastening means that make it possible to fasten the housing 16 to the frame 4 of the racket 1.

When the cover 223 of the butt cap 22 covers the body 221, the butt cap 22 tightly closes the handles 2 and 102, on the side of the free end 21.2, which protects the electronic circuit 20 from rain or the player's sweat. Furthermore, the cover 223 of the butt cap 22 allows the player, when the cover 223 covers the body 221, to use the buttons 15.1 and 15.2. Indeed, the cover 223 is made from a material with a flexibility allowing the player, when he presses on the cover 223, to deform it to actuate the buttons 15.1 and 15.2. He can thus activate or deactivate the measuring system, and activate or deactivate data exchanges via the antenna 11, during play. The button 15.2 also makes it possible to split the recording into several play sequences: when the measuring system is active and each time the player pushes that button 15.2, a time marker is created, in order to separate the recorded data into several play sequences. This option makes it possible to analyze the play based on the chosen sequence.

The button 15.3 is not accessible when the cover 223 of the butt cap 22 covers the body 221. That button 15.3 makes it possible to reset the measuring system. To actuate it, it is necessary to remove the cover 223 and press on that part 5, which deforms and comes into contact with the button 15.3. In that configuration, it is also possible to access the connector 17.

In the described examples, two sensors are fastened to the housing 16, i.e., the sensors 14.2 and 14.3. Alternatively, a single sensor is fastened to the housing 16, i.e., the sensor 14.1, 14.2 or 14.3. In another alternative, all three sensors 14.1, 14.2 and 14.3 are fastened to the housing 16. Thus, at least one of the sensors 14.1, 14.2 and 14.3 is fastened to the housing 16. 

1-16. (canceled)
 17. A tennis racket, including: a head including a frame surrounding strings, a gripping handle, a vibration sensor, a triaxial linear acceleration sensor, and a triaxial angular speed sensor.
 18. The tennis racket according to claim 17, further including means for storing data recorded by the sensors, and means for transmitting data recorded by the sensors.
 19. The tennis racket according to claim 17, wherein the vibration sensor is fastened to the head of the racket.
 20. The tennis racket according to claim 17, wherein the head includes connecting branches that connect the strings to the handle, and the vibration sensor is fastened on a connecting zone of the connecting branches.
 21. The tennis racket according to claim 17, wherein the triaxial linear acceleration sensor and the triaxial angular speed sensor are secured to the handle.
 22. The tennis racket according to claim 17, wherein at least one electrical circuit associated with the sensors is fastened to a removable housing that is removably fastened to the frame of the racket.
 23. The tennis racket according to claim 22, wherein at least one of the sensors is also fastened to the removable housing.
 24. The tennis racket according to claim 22, wherein the handle is hollow and contains the removable housing.
 25. The tennis racket according to claim 22, wherein the electronic circuit is equipped with the triaxial linear acceleration sensor and the triaxial angular speed sensor and fastened to the removable housing.
 26. The tennis racket according to claim 22, wherein the removable housing is fastened to the frame of the racket using fastening elements.
 27. The tennis racket according to claim 22, wherein the fastening elements are oriented perpendicular to the handle.
 28. The tennis racket according to claim 22, wherein the hollow body of the handle comprises two inner rails parallel to the handle and wherein the removable housing comprises two longitudinal slots.
 29. The tennis racket according to claim 22, further including a butt cap fastened to the housing, at the free end of the handle, using removable fastening means oriented parallel to the handle.
 30. The tennis racket according to claim 22, further including a rechargeable battery that powers the electronic circuit.
 31. The tennis racket according to claim 22, further including a butt cap fastened to the housing, at the free end of the handle, and which tightly closes the handle while allowing manipulation of the control buttons of the electronic circuit.
 32. The tennis racket according to claim 22, wherein the vibration sensor is glued on the frame of the racket and is connected, using electrical wires, to an electronic circuit fastened to the removable housing.
 33. The tennis racket according to claim 18, wherein the means for transmitting data include wired connecting means.
 34. The tennis racket according to claim 33, wherein the wired connecting means include an electrical connector of the USB type.
 35. The tennis racket according to claim 18, wherein the means for transmitting data include wireless transmission means.
 36. The tennis racket according to claim 35, wherein the wireless transmission means include an antenna of the Bluetooth type.
 37. The tennis racket according to claim 19, wherein the vibration sensor is fastened to the head of the racket by adhesion.
 38. The tennis racket according to claim 26, wherein the fastening elements include screws. 